Drain feedtube for hydraulic motor

ABSTRACT

A telescopic feedtube for draining fluid from the housing of a motor carried on the end of an extensible boom or the like, separate from feedtubes which convey motive fluid to and from the motor, there being provided a reciprocating hydraulic motor for the boom controlled by a valve which is also connected to selectively supply fluid to the drain tube during retracting of the actuator for the purpose of providing a retracting force on the feedtube when the actuator is retracted minimizing the tendency of the drain feedtube to collapse.

United States Patent [72] lnventor John T. Parrett 3,207,044 9/1965 Hall A I N gggtzg Primary Examiner-Martin P. Schwadron D. 5 1969 Assistant Examiner-R. Lazarus I 4 1 Patented June 22, Attorney Hofgren, Wegner, Allen, Stellman and McCord [73] Assignee Koehring Company [54] DRAIN FEEDTUBE FOR HYDRAULIC MOTOR 8 Claims, 2 Drawing Figs.

1 ABSTRACT: A telescopic feedtube for draining fluid from the 2l2/55 housing of a motor carried on the end of an extensible boom [5 I 1 Int. CL F!) 11/00 or the like separate from feedtubes which cgnvey motive fluid to and from the motor there being provided a reciprocating 212/ hydraulic motor for the boom controlled by a valve which is also connected to selectively supply fluid to the drain tube [56] ammo CM during retracting of the actuator for the purpose of providing a UNITED STATES PATENTS retracting force on the feedtube when the actuator is retracted 3,31 8 I99 5/1967 Pa rett 91/462 minimizing the tendency of the drain feedtube to collapse.

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T Q fl-m/f 17 97 62 /6E% I w L W 18 L I i "'12? g 14 /0 j A DRAIN FEEDTUBE FOR HYDRAULIC MOTOR BACKGROUND OF THE PRESENT INVENTION Hydraulic motors have been provided in the past on the end of extensible booms or the like for the purpose of performing certain work operations. The motor is supplied hydraulic fluid from a pump located on a relatively stationary portion of the frame so that either flexible tubing or telescopic tubing must be provided in order to supply fluid to or return fluid from the motor since the motor is extended and retracted by the boom.

In many types of hydraulic motors employed in this environment, such as reciprocating piston-swashplate motors, the motor housing serves as a reservoir for collecting leakage fluid from the motor. The pressure of fluid in the motor casing is considerably below that in the return line from the motor so that it is desirable that the casing be drained through a line separate from the return line.

SUMMARY OF THE PRESENT INVENTION In accordance with the present invention a feedtube is provided for a hydraulic actuator carried by an extensible boom or the like for the purpose of returning drain fluid from the motor casing to a reservoir. While the capacity requirements of such a feedtube are relatively small and thus the feedtubes may be of relatively small diameter, they are necessarily of considerable length and they tend to sag under their own weight. According to the present invention the feedtube consists of an inner tube having a piston on the end thereof slidable in and hydraulically communicating with an outer tube. As the boom is retracted by a reciprocating piston hydraulic actuator, the feedtubes, connected to the boom sections, will also retract. However, the friction between the piston on the inner feedtube and the outer feedtube resists this retracting motion and the feedtubes tend to collapse, particularly if they are of significant length.

To obviate this problem and in accordance with the present invention, the drain feedtube itself acts as a hydraulic actuator during the retracting stroke of the main boom actuator so that the feedtube tends to retract itself during this period, preventing the retracting boom from applying a collapsing force on the feedtube sections.

Toward this end the chamber within the outer feedtube defined by the inner feedtube piston on the "retract" side thereof is connected to the main control valve for the boom actuator so that whenever the boom is retracted this chamber is supplied fluid under pressure thereby retracting the drain feedtube.

Fluid under pressure from the main actuator, rather than drain fluid itself, is used to retract the drain feedtube since the drain fluid or case pressure is generally only slightly above atmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration of a hydraulic circuit employing the present drain feedtube system; and

FIG. 2 is a longitudinal section of a drain feedtube according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing and particularly FIG. 1, which is diagrammatic in form, an extensible boom is illustrated having a first boom section 12 supported on a relatively stationary frame (not shown) with a second boom section 14 extendible with respect thereto. The boom 14 may be carried by a piece of mobile equipment, for example. The boom 10 is extended and retracted by an hydraulic actuator 16 having a cylinder section 17 extendible with respect to a piston and rod section 18 fixed to the boom section 12. The cylinder section 17 is connected by suitable mechanical connection, such as indicated at 20, to drive the boom section 14. For the purpose of supplying fluid to extend and retract the hydraulic actuator 16 a four-way control valve 22 is provided which selectively supplies fluid from a pump 24 to the actuator through either an extend line 26 or a retract line 27 connected-to the piston and rod section 18. The actuator 16 is constructed so that when fluid is supplied through line 26 the actuator section 17 will extend with respect to actuator section 18 and when fluid is supplied through line 27 the actuator section 17 will retract with respect to section 18 retracting the boom 10.

Carried by the end of boom section 14 is a hydraulic motor 28 which may take the form of a multiple piston swashplate motor. These motors are well known in the art to include a valve plate having inlet and outlet ports therein against which a rotary cylinder block bears, having cylinders therein which serially communicate with the inlet and outlet ports. Pistons are provided slidable in the cylinders and are reciprocated by a cam or swashplate member. In such hydraulic units there is a certain amount of leakage from the hydraulic cylinders as well as between the cylinder block and the valve plate. For the purpose of collecting this leakage fluid, housing 30 for the motor is permitted to act as a reservoir for this leakage fluid.

For the purpose of supplying fluid to drive the motor 28 in either direction of rotation a motor control valve 32 is provided which is a four-way close center valve similar in construction to valve 22. Control valve 32 selectively connects lines 34 or 36 to pump 38 or drain line 39 so that either line 34 or 36 may be the pressure conduit or the return conduit. Conduits 34 or 36 are connected to deliver fluid relative to motor 28 through extendible feedtubes 40 and 42 which are in turn connected to the inlet and outlet ports of the motor 28 through conduits 44 and 46. Each of the feedtubes 40 and 42 includes an outer feedtube member 47 which telescopically receives an inner feedtube member 42 and 49. The feedtube members 47 are fixed by suitable mechanical interconnections indicated at 51 to boom section 12 while feedtube sections 49 are connected by suitable mechanical interconnection 53 to boom section 14. In this manner, the feedtube sections 49 extend and retract with the boom section 14 while at all times maintaining fluid interconnection between the conduits 34, 36 and 44, 46 so that the motor 28 may be driven, during movement of the boom 10, in either direction of rotation or may be driven when the boom is in any of extended positions.

For the purpose of returning drain fluid from the interior of the motor housing 30 to reservoir 55 a drain feedtube assembly 58 is provided connected to the motor housing 30 through a suitable conduit 60. The drain feedtube assembly 58 consists of an outer tube 62 carried by boom section 12 and a telescopically arranged inner tube 63 carried by boom section 14 and extensible therewith. As shown more clearly in FIG. 2, the outer feedtube 62 includes an elongated sleeve 65 having a threaded fitting 67 welded at its right end and a sleeve fitting 68 surrounding and welded to its left end. Sleeve fitting 68 threadedly receives an end cap 69. A sleeve 71 is provided between a bushing 72 and cap 69 for preventing the egress of fluid from the left end of the feedtube sleeve 68.

The inner tube 63 includes a narrow elongated tube 74 slidably received in bore 76 of cap 69 and bore 77 of bushing 72 and carries at its right end a piston assembly 81 having piston rings 89 slidably engaging the interior of outer tube or sleeve 65. A suitable threaded fitting 90 is fixed to the left end of tube 74 and is adapted to be connected to conduit 60. Fitting 67 receives a suitable conduit directing drain flow to reservoir 55.

Fluid to be drained in the housing 30 is in the range of 15 to 50 p.s.i., while return flow in the return one of the feedtubes 40, 42 may be as high as 300 p.s.i. because of the resistance created by the various valves in the path of outlet flow from motor 28. Therefore, the drain feedtube 58 provides an unrestricted return path for excess drain. fluid in the motor ing 30. Drain fluid flowing into conduit 60 passes t fitting 90 into tube 74 which opens directly into chamber the outer tube from where fluid passes through fitting 67 into reservoir 55.

Because of the great length of the tubes 74 and 65 compared to their diameter, there is a tendency for them to collapse when the actuator 16 is retracted. This retracting force is in part due to the frictional resistance to retracting of the feedtube 58 by the piston assembly 81 and more specifically by piston rings or seals 89. To obviate this problem chamber 96 defined by the piston assembly 61 within the outer feedtube 62 is pressurized with fluid from the main actuator pump 26 whenever the main actuator 16 is retracted. In this manner the feedtube 58 retracts itself rather than being retracted by the boom 10 or actuator 16 thus eliminating the tendency for the feedtube 58 to collapse under this external retracting force.

Toward this end the chamber 96 communicates with the main actuator retract line 27 through conduit 97 which is connected to port 98 shown in F l0. 2. Thus whenever the control valve 22 is shifted to the left pressurizing retract line 27 fluid will be ported to feedtube chamber 96 pressurizing the left side of piston assembly 81 and retracting the inner tube 63 with respect to the outer tube 62 by pressurizing the left side of piston assembly 81. This places the sleeves or tubes 74 and 65 in tension eliminating the tendency for them to collapse. It is readily apparent that in the absence of pressurization of the chamber 96 during the retract stroke that the force of the retracting boom acting rightwardly on the inner tube 63 from fitting 90, opposed by the resistive force of piston 8R sliding in sleeve 65, would place both tubes 74 and 65 in compression tending to collapse them. This collapsing force is eliminated through the pressurization of chamber 96 with sufficient fluid pressure.

Chamber 96 is connected to the main actuator pump 24 through line 97 and thus a relatively high pressure is available to pressurize, e.g. 1,000 p.s.i., chamber 96, far above the pressure of drain fluid returning through conduit 60.

I claim:

ll. A hydraulic system, comprising: a first member, a second member, means for extending and retracting said first member with respect to saidsecond member, fluid motor means associated with said second member, fluid supply means for delivering motive fluid to drive said motor means, fluid return means for returning motive fluid from said motor means, and means for draining fluid from said motor means including a first feedtube and a second feedtube in telescopic relation therewith, and fluid operable means for preventing collapsing of said feedtubes.

2. A hydraulic system, comprising: a first member, a second member, means for extending and retracting said first member with respect to said second member, fluid motor means associated with said second member, fluid supply means for delivering motive fluid to drive said motor means, fluid return means for returning motive fluid from said motor means, and means for draining fluid from said motor means including a first feedtube and a second feedtube in telescopic relation therewith, the inner one of said feedtubes having piston means thereon, and means for supplying fluid to said piston means on the side thereof tending to retract said feedtubes to prevent collapsing of the feedtubes when the second member is retracted with respect to said first member.

3. A hydraulic system as defined in claim 2, said first and second member including a telescopic hydraulic actuator, said motor means being carried by said second member, said motor means including a housing which serves as a reservoir for motor leakage fluid, means connected said feedtubes to receive drain fluid from said motor housing.

4. A hydraulic system as defined in claim 2, wherein said means for supplying pressure to said piston means includes means for supplying pressure at a value higher than the pressure of drain fluid.

5. A hydraulic system as defined in claim 2, said means for supplying fluid to said piston being operable when said second member retracts with respect to said first member.

6. A hydraulic system as defined in claim 5, said first and second members being extendable and retractable by a fluid operable reciprocating actuator, valve means for supplyin fluid relatively to opposite sides of the actuator to extend an retract the same, said valve means being connected to supply fluid under pressure to said means for supplying fluid to said feedtube piston means only when supplying fluid to retract said actuator.

7. A hydraulic system as defined in claim 3, said first and second members being extendible and retractable by a hydraulic actuator, one of said feedtubes being fixed with respect to one of said members, the other of said feedtubes being fixed with respect to the other of said members, one of said feedtubes having said piston means thereon slidable in the other of said feedtubes, said piston means defining a retract fluid chamber in the other of said feedtubes, said means for supplying fluid to said feedtubes being connected to supply fluid to said chamber.

8. A hydraulic system, comprising: a hydraulic actuator having first and second relatively extendible members, fluid operable motor means carried by one of said members, said motor having a drain reservoir, means for supplying fluid to said motor means, means for returning fluid from said motor means, elongated telescopic feedtube means separate from said return means for draining fluid from said drain reservoir, and means tending to retract said feedtube means to prevent collapse thereof. 

1. A hydraulic system, comprising: a first member, a second member, means for extending and retracting said first member with respect to said second member, fluid motor means associated with said second member, fluid supply means for delivering motive fluid to drive said motor means, fluid return means for returning motive fluid from said motor means, and means for draining fluid from said motor means including a first feedtube and a second feedtube in telescopic relation therewith, and fluid operable means for preventing collapsing of said feedtubes.
 2. A hydraulic system, comprising: a first member, a second member, means for extending and retracting said first member with respect to said second member, fluid motor means associated with said second member, fluid supply means for delivering motive fluid to drive said motor means, fluid return means for returning motive fluid from said motor means, and means for draining fluid from said motor means including a fIrst feedtube and a second feedtube in telescopic relation therewith, the inner one of said feedtubes having piston means thereon, and means for supplying fluid to said piston means on the side thereof tending to retract said feedtubes to prevent collapsing of the feedtubes when the second member is retracted with respect to said first member.
 3. A hydraulic system as defined in claim 2, said first and second member including a telescopic hydraulic actuator, said motor means being carried by said second member, said motor means including a housing which serves as a reservoir for motor leakage fluid, means connected said feedtubes to receive drain fluid from said motor housing.
 4. A hydraulic system as defined in claim 2, wherein said means for supplying pressure to said piston means includes means for supplying pressure at a value higher than the pressure of drain fluid.
 5. A hydraulic system as defined in claim 2, said means for supplying fluid to said piston being operable when said second member retracts with respect to said first member.
 6. A hydraulic system as defined in claim 5, said first and second members being extendable and retractable by a fluid operable reciprocating actuator, valve means for supplying fluid relatively to opposite sides of the actuator to extend and retract the same, said valve means being connected to supply fluid under pressure to said means for supplying fluid to said feedtube piston means only when supplying fluid to retract said actuator.
 7. A hydraulic system as defined in claim 3, said first and second members being extendible and retractable by a hydraulic actuator, one of said feedtubes being fixed with respect to one of said members, the other of said feedtubes being fixed with respect to the other of said members, one of said feedtubes having said piston means thereon slidable in the other of said feedtubes, said piston means defining a retract fluid chamber in the other of said feedtubes, said means for supplying fluid to said feedtubes being connected to supply fluid to said chamber.
 8. A hydraulic system, comprising: a hydraulic actuator having first and second relatively extendible members, fluid operable motor means carried by one of said members, said motor having a drain reservoir, means for supplying fluid to said motor means, means for returning fluid from said motor means, elongated telescopic feedtube means separate from said return means for draining fluid from said drain reservoir, and means tending to retract said feedtube means to prevent collapse thereof. 